1. Field of the Invention
The present invention relates to a photographic printing apparatus in which a negative film of continuous length is successively fed out and images thereon are printed on photographic paper.
2. Description of the Prior Art
A typical conventional photographic printing apparatus used to print a negative film of continuous length has hitherto been arranged such that the negative film previously wound on a supply unit is fed out to a take-up unit while passing through a negative film carrier, and images on the negative film passing over a printing gate aperture formed in the negative film carrier are sequentially printed on a roll of photographic paper.
The size of the printing gate aperture of the negative film carrier in the above-described photographic printing apparatus is generally determined in such a manner that the aperture can correspond to either a negative film having images of the full size (24.times.36 mm) or a negative film having images of the half size (18.times.24 mm), which is 1/2 of the full size. In view of this fact, a photographic printing apparatus having a negative film carrier which is capable of corresponding to both full- and half-size images has heretofore been proposed (examples of this type of photographic printing apparatus include Japanese Patent Laid-Open No. 129029/1978).
In such a photographic printing apparatus, it is necessary to change an optical system with another in correspondence with the size of the images on a negative film which is to be subjected to a printing operation. For this reason, it is general practice to dispose a plurality of optical systems about the center of rotation and to allow these optical systems to successively coincide with the printing gate aperture, thereby enabling an effective printing operation. However, light receivers for measuring, for example, the quantity of light passing through a negative film and density variations are disposed on the right and left sides of the printing gate aperture. The light receivers may, therefore, interfere with the moving locus of the optical systems, thus disadvantageously obstructing an effective changing operation for the optical systems.
In order to overcome such a disadvantage, a structure has heretofore been proposed in which the light receivers are respectively mounted on the distal ends of pivoting arms, and when the optical systems are changed one with another, the pivoting arms are moved to thereby retract the light receivers from the moving locus of the optical systems (examples of this structure include Japanese Utility Model Laid-Open No. 63347/1982). If such a structure is employed, however, the structure for supporting the light receivers is complicated, and it is necessary to provide additional means, such as a positioning device.
Further, in the case where automatic photometry is carried out and, at the same time, an operator corrects printing conditions by visually examining a portion of a negative film, held in the printing gate aperture, from the front side of the negative film carrier, the operator is given only a disadvantageously narrow field of view defined between a plurality of light receivers. For this reason, there has been a need to improve the photometric environment.